View Compilation Error

0_0_19479107_31945.cpp: In function 'int main()':
0_0_19479107_31945.cpp:16:32: error: 'elseif' was not declared in this scope
 elseif(op[i]>='0' && op[i]<='9')c=1;
                                ^
0_0_19479107_31945.cpp:21:18: error: 'elseprintf' was not declared in this scope
 elseprintf("NO\n");}
                  ^